The building at 160 N. Main dates from the late 1960s and county Chief Administrative Officer Harvey Kennedy says the aging of systems such as heating and air-conditioning makes the renovation necessary.

"It's got to be done now or later, and the costs will only escalate if we put this off," he said.

The administration's proposal likely will trigger arguments over spending priorities -- in March, commissioners including Terry Roland said they were reluctant to spend so much money on the project.

And Commissioner Mike Ritz said he'd like to explore the option of moving county workers to space in commercial buildings.

However, Kennedy said Tuesday that's not feasible.

The low bidder on the renovation project was Chattanooga-based EMJ Construction, at $19.1 million. Memphis-based archimania has a separate contract for architectural and engineering design work.

Kennedy said he expects commissioners to ask questions about the participation of minority-owned firms.

He said 32 percent of the project is expected to go to locally owned small businesses, but that the county has no program to regulate minority participation in such projects. "Without a program, we can't really specify a minority participation, but (the contractor knows) they're thoroughly expected to be inclusive of everyone."

Among other things, the contractor would rearrange the building's office space, boost compliance with the Americans with Disabilities Act and improve bathrooms -- currently, several floors in the 11-story building have either a men's restroom or a women's restroom, but not both.

The contractor also would replace the bench-like heating and air-conditioning units that hug the walls in many rooms. Using more modern equipment would free up significant amounts of space, enabling the government to bring in employees who currently work in other county-owned buildings, Kennedy said.

Kennedy also said that replacing building systems and windows would reduce energy costs.

"We'll be saving a tremendous amount on maintenance as well," he said. "Everything's starting to age."

Workers would overhaul two floors at a time in a process that would take about two years. County contractors created an elaborate plan to move employees from place to place.

If the County Commission approves the agreement, the work would begin in August or September, Kennedy said.

Luttrell's administration is asking commissioners to pay for the project by amending the capital improvement budget for the current fiscal year, which ends June 30. The budget already lists $5 million for the project, and the county can cover the rest by shifting projects to the next fiscal year and eliminating plans to build a new, joint city-county 911 call center, Kennedy said.

Commissioners will hear a presentation at the 9 a.m. public works committee today and may vote on it at the full commission on Monday.